Moderate vasomotor response to acetylcholine provocation test as an indicator of long-term prognosis

The acetylcholine (ACh) provocation test (ACh-test) is used for the diagnosis of vasospastic angina (VSA). However, subjects often show a moderate spasm (MS) response for which diagnosis of VSA is not definitive, and the clinical significance of this response is unknown. We assessed moderate coronary vasomotor response to the ACh test as an indicator of long-term prognosis. A total of 298 consecutive patients who underwent the ACh test for suspected VSA were retrospectively investigated. Coronary spasm severity after intracoronary administration of isosorbide dinitrate was evaluated by measuring epicardial coronary artery diameter reduction after ACh injection. Patients were divided into three groups according to the diameter reduction during the ACh test: severe spasm (SS) showing ≥75 % diameter reduction, MS showing ≥50 % diameter reduction, and others (N). In Kaplan-Meier analysis, the major adverse cardiac event (MACE) rates with a median follow-up of 4.6 years were significantly worse in SS (11.1 %) and MS (8.5 %) than N (1.9 %), (SS vs N; P = 0.009, MS vs N; P = 0.029). Significant difference in MACE rates was not observed between SS and MS (P = 0.534). Cox regression analysis revealed that MS remained an independent predictor of MACE after adjustment for other confounders (HR: 7.18, 95 % CI 1.42-36.4, P = 0.017). Patients with MS by ACh test had a cardiac event rate comparable with that of patients with SS and significantly worse than that of patients with normal vasomotor responses.